Symmetrical copy lenses

ABSTRACT

A series of four element photographic lenses for use at or near unity magnification, the lenses being in the form either of four elements in a symmetrical pattern or two elements and a mirror.

Lynn L. Van Orden, Holley, N.Y.

Bausch 8: Lornb Rochester, NY.

Oct. 28, 1971 Inventor:

Assignee: Incorporated,

Filed:

Appl. No.:

11.5. CI. ..350/221, 350/202 1m. Cl. ..G02b 9/36, G02b 17/08 Field of Search ..350/221, 202

TW we May 8, 1973 [56] References Cited UNITED STATES PATENTS 2,865,252 12/1958 Rciss ..350/22l 3,370,904 2/1968 Hudson ..350/22l 3,402,003 9/1968 McFarland ..350/202 UX Primary Examiner-John K. Corbin Att0rney-Frank C. Parker et al.

[57] ABSTRACT A series of four element photographic lenses for use at or near unity magnification, the lenses being in the form either of four elements in a symmetrical pattern or two elements and a mirror.

16 Claims, 2 Drawing Figures SYMMETRICAL COPY LENSES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention lies in the field of symmetrical four component lenses of the kind having singlet positive meniscus lenses in the first and fourth positions and singlet negative meniscus lenses in the second and third positions, all such meniscus lenses being concave toward a central aperture stop.

2. Description of the Prior Art Lenses of the shapes here in question are shown in US. Pat. Nos. 3,449,040 and 3,507,560. Such lenses are often employed in copy devices for use at or near unit magnification in which case they may consist either of four lenses of which the first and fourth lenses and the second and third lenses are respectively identical but reversed, or they may consist of only a first and second lens with a mirror aligned in the central aperture stop so that an off axis ray proceeding through the first and second lens to the mirror will be reflected back through the second and the first lenses in the same way as if it were passing through the third and fourth lenses. Accordingly, with such symmetrical lenses a complete description is given merely by the radii, respectively, of the first and second lenses, the thicknesses, respectively, of the first and second lenses, the spaces separating the first lens from the second and the second lens from the stop and the respective glass types.

SUMMARY OF THE INVENTION l have discovered within the field of symmetrical, four single element lenses of the above description a pattern of lens shapes, thicknesses, spaces and glass types which is richly productive of lenses characterized by good image resolution and freedom from aberrations at relatively high apertures.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a optical schematic of the lens of my invention.

FIG. 2 is an optical schematic of a version of the lens of my invention wherein a mirror is replacing the second half of the lens.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As may be seen from FIG. 1 the lens of my invention consists of four elements all of which are meniscus lenses concave toward a central stop and being designated respectively I-IV of which it may be seen that lenses I and IV are of identical shape but reversed, and lenses II and III are likewise of identical shape but reversed. Lenses I and IV are both positive singlet meniscus lenses of relatively low index, high dispersion glass while lenses II and III are negative singlet meniscus lenses of relatively high index glass and relatively low dispersion. Lens I is defined by radii R, and R, and a thickness 1,, these parameters being identical respectively to the radii R, and R, and the thickness 1, of the lens IV. Lens II is defined by radii R, and R, and the thickness 2, which correspond respectively to the radii R, and R, and the thickness 1, of the lens III. The lenses I and IV and the lenses II and II, respectively, are made from glasses of the same refractive indices,, n,,, and as well as of the same Abbe numbers 11, and P1, describing the relative dispersions. In addition, the lens II is airspaced very narrowly from the Lens I, which space is designated 8,. The space S, is of identical magnitude with the space designated S, by which the lens IV is airspaced narrowly from the lens III, and the lenses II and III are spaced from a central aperture stop by spaces S, and 8,, respectively, which are equal to one another.

As noted above, because of the symmetry of the kind of lenses here described the lenses Ill and IV can, for certain purposes and in certain applications, be replaced by a mirror in the position of the aperture stop as is shown in FIG. 2. Therefore a lens of the kind here in question is completely described by enumeration of the first four radii R, through R,, the first two thicknesses t, and 2,, the first two spaces S, and 8,, the refractive indices n and ri of the first two lenses and the Abbe number v, and v, of the first two lenses. Accordingly, I have found that symmetrical lenses of the type here disclosed constructed in accordance with the parameters set forth in Table I below produce images of high quality, good image resolution, maximum freedom from aberrations and good contrast. The radii, thicknesses and spaces are disclosed as decimal ratios of the focal length. The refractive indices 71,, and the Abbe numbers 11 are given directly.

TABLEI l 2 3 4 5 6 R, .2l7 .217 .208 .2ll .2ll .2ll R; .435 .439 .4l6 .424 .424 .424 .207 .213 .203 2.04 .203 .204 R, .147 .148 .143 .143 .143 .143 1, .048 .051 .045 .040 .045 .040 7, .030 .028 .028 .029 .029 .029 S1 .0004 .0004 .0005 .0005 .0005 .0005 s. .095 .093 .093 .092 .093 .093 ,1... 1.020 1.020 1.020 1.020 1.020 1.020 n 1.720 1.073 1.720 1.720 1.720 1.720 v, 60.3 60.3 60.3 60.3 60.3 60.3 v, 29.3 32.2 29.3 29.3 29.3 29.3

The six lenses specified in the table above give outstanding performance at apertures as large as 1745 If in the manufacture of the individual lenses and their mounting components certain variations in any of the numbers listed were to occur, an optical technician of ordinary skill would nonetheless be able to assemble a substantially symmetrical lens from such varied components. If such variations were within certain ranges, the performance of the lens so assembled would still meet certain commercial standards and be useful for their intended purpose, although perhaps at smaller apertures, as for example fl 16 or 1722. If all variations in characteristics were kept within the ranges given below in Table II, useful lenses may be assembled from the components.

TABLE II .207: a. 5 K .217: .415: a, S .445: 1. R. .215: .140: R. 5 .149: .044: I, s .052: .027: s r, 5 .031: .0004: s. s .0000: .090: s s, 5 .090: 1.015 s 7-,. 1.025 1.073 n... 5 1.721 57.13 s v. 5 02.1; 27.8 =2 v, S 33.0

1 claim:

1. A symmetrical lens having four singlet meniscus elements symmetrical about and concave toward a central stop, the first and second elements having radii, proceeding toward the center, R,, R,, R,, and R and thicknesses, proceeding toward said center, t, and 1,, said lenses being spaced apart by a space S, and said second lens being spaced from said center by a space 8,, said radii, thicknesses; and spaces being expressed as a fraction of the focal length f falling within the ranges listed below and said elements being of glass having characteristic refractive indices n and n and Abbe numbers v, and v, falling within the ranges listed in the table below:

.207r R 1; .217: .41 sr R, s .44sr .193: R, .2l5f .140r R s 1.49r .044: s r, s .oszr .027t r, s .03lt .0004: s, s .ooosr .090: s s, s 0.9 1.615 s 1.625 1.673 s n s 1.721 57.8 s v, s 62.8 27.8 v, s 33.0

2. The lens of claim 1 having values substantially as listed below:

R, .2171 R, .4351 R, .2071 R, .l47f t, .048l' I, .030t' S, .00041' S, .0951 n 1.620 n 1.720 1!, 60.3 v, 29.3

3. The lens of claim 1 having values substantially as listed below:

4. The lens of claim 1 having values substantially as listed below:

R, .2081 R| .416t' R, .2031 R, 1431' t, .0451 I, .0281 S, .00051 S, .0931 n 1 .620 n 1 .720 v, 60.3 v, 29.3

5. The lens of claim 1 having values substantially as listed below:

R, .2 1 If R, .42

6. The lens of claim 1 having values substantially as listed below:

R, .2 1 If R, .4241" R, .203f R, l 43f t, .0451 r, .0291 S, 00051 S, .09 If n 1 .620 n 1 .7 20 v, 60.3 v, 29.3

7. The lens of claim 1 having values substantially as listed below:

R, .2 1 If R, .424! R; .2041 R, 1431' t. .046f l, .0291" S, .00051 S, .09 31' n 1 .620 n l .720 v, 60.3 v, 29. 3

8. A retroreflective lens for use at or near unit magnification having first and second singlet meniscus elements and a plane mirror, said elements being concave toward said mirror and having radii, proceeding toward said mirror, R,, R,, R,, R and thicknesses, proceeding toward said mirror, t, and t,, said first element being separated from said second element by a space S,, and said second element being separated from said mirror by a space 8,, said radii, thicknesses and spaces being expressed as a fraction of the focal length f, falling within the ranges listed below, and said elements being of glass having characteristic refractive indices, n and and Abbe numbers v, and v,, falling within the ranges listed in the table below:

listed below:

10. The lens of claim 8 having values substantially as listed below:

listed below:

.2081 .4161' .203f .1431 0.451 .028f .0005f .0931' 1.620 1.720 60.3 29.3

12. The lens of claim 8 having values substantially as listed below:

13. The lens of claim 8 having values substantially as listed below:

14. The lens of claim 8 having values substantially as listed below:

R .21 If R, .42 R, .2041 R .1431 1 .0461 r, .0291 S .00051' S, .0931 n 1.620 n 1.720 v, 60.3 v, 29.3

15. A symmetrical lens having four singlet meniscus elements symmetrical about and concave toward a central stop, the first and second elements having radii, proceeding toward the center, R,, R,, R and R and thicknesses, proceeding toward said center, r and 1,, said lenses being spaced apart by a space S, and said second lens being spaced from said center by a space 8,, said radii, thicknesses, and spaces being expressed as a fraction of the focal length f falling within the ranges listed below and said elements being of glass having characteristic refractive indices n, and n and Abbe numbers v, and v, falling within the ranges listed in the table below:

.ozsr s R. s .217f .4161 s R, s .439r .203r s R, s .213! .143: R. 5 .mar 0- a 1. s .05 1f 0.28! s 1, S .030r .oo04r S. s .ooosr .092r S, s .ossr 1.620 11 1.673 s n: s 1.720 60.3 v,

29.3 s v, s 32.2

16. A retroreflective lens for use at or near unit magnification having first and second singlet meniscus elements and a plano mirror, said elements being concave toward said mirror and having radii, proceeding toward said mirror, R R,, R and R and thicknesses, proceeding toward said mirror, t and r,, said first element being separated from said second element by a space S and said second element being separated from said mirror by a space 8,, said radii, thicknesses and spaces being expressed as a fraction of the focal length f, falling within the ranges listed below, and said elements being of glass having characteristic refractive indices, n and u and Abbe numbers 11 and v,, falling within the ranges listed in the table below.

.208: s R, s .217r .4l6t' s R, s .439f .2031 s R. s .213: .l43f s R. s .1481 .045: z 1. a .05 it .ozsr 1, s .o3or .ooo4r f s, s most 2% s .09sr

. II 1.673 s n: s 1.720 60.3 a v 29.3 s v, s 32.2 

1. A symmetrical lens having four singlet meniscus elements symmetrical about and concave toward a central stop, the first and second elements having radii, proceeding toward the center, R1, R2, R3, and R4, and thicknesses, proceeding toward said center, t1 and t2, said lenses being spaced apart by a space S1 and said second lens being spaced from said center by a space S2, said radii, thicknesses, and spaces being expressed as a fraction of the focal length f falling within the ranges listed below and said elements being of glass having characteristic refractive indices nD1 and nD2 and Abbe numbers v1 and v2 falling within the ranges listed in the table below: .207f < OR = R1 < OR = .217f .415f < OR = R2 < OR = .445f .198f < OR = R3 < OR = .215f .140f < OR = R4 < OR = 1.49f.044f < OR = t1 < OR = .052f.027f < OR = t2 < OR = .031f .0004f < OR = S1 < OR = .0006f .090f < OR = S2 < OR = 0.96f1.615 < OR = nD1 < OR = 1.6251.673 < OR = nD2 < OR = 1.72157.8 < OR = Nu 1 < OR = 62.827.8 < OR = Nu 2 < OR = 33.0
 2. The lens of claim 1 having values substantially as listed below: R1.217f R2.435fR3.207fR4.147ft1.048ft2.030fS1.0004fS2.095fnD11.620nD21.72 0 Nu 160.3 Nu 229.3
 3. The lens of claim 1 having values substantially as listed below: R1.217f R2.439fR3.213fR4.148ft1.051ft2.028fS1.0004fS2.093fnD11.620nD21.67 3 Nu 160.3 Nu 232.2
 4. The lens of claim 1 having values substantially as listed below: R1.208fR2.416f R3.203fR4.143ft1.045ft2.028fS1.0005f S2.093fnD11.620nD21.720 Nu 160.3 Nu 229.3
 5. The lens of claim 1 having values substantially as listed below: R1.211fR2.424fR3.204fR4.143ft1.046ft2.029fS1.0005fS2.092fnD11.620 nD21.720 Nu 160.3 Nu 229.3
 6. The lens of claim 1 having values substantially as listed below: R1.211f R2.424f R3.203fR4.143ft1.045ft2.029f S1.0005f S2.093fnD11.620nD21.720 Nu 160.3 Nu 229.3
 7. The lens of claim 1 having values substantially as listed below: R1.211fR2.424fR3.204f R4.143ft1.046ft2.029fS1.0005fS2.093fnD11.620 nD21.720 Nu 160.3 Nu 2 29.3
 8. A retroreflective lens for use at oR near unit magnification having first and second singlet meniscus elements and a plano mirror, said elements being concave toward said mirror and having radii, proceeding toward said mirror, R1, R2, R3, R4, and thicknesses, proceeding toward said mirror, t1 and t2, said first element being separated from said second element by a space S1, and said second element being separated from said mirror by a space S2, said radii, thicknesses and spaces being expressed as a fraction of the focal length f, falling within the ranges listed below, and said elements being of glass having characteristic refractive indices, nD1 and nD2, and Abbe numbers Nu 1 and Nu 2, falling within the ranges listed in the table below: .207f < or = R1 < or = .217f.425f < or = R2 < or = .445f.198f < or = R3 < or = .215f.140f < or = R4 < or = .149f.044f < or = t1 < or = 0.52f.027f < or = t2 < or = .031f.0004f < or = S1 < or = .0006f.090f < or = S2 < or = .096f1.615 < or = nD1 < or = 1.6251.673 < or = nD2 < or = 1.721 57.8 < or = Nu 1 < or = 62.8 27.8 < or = Nu 2 < or = 33.0
 9. The lens of claim 8 having values substantially as listed below: R1.217f R2.435fR3.207fR4.147ft1.048ft2.030fS1.0004fS2.095fnD11.620nD21.72 0 Nu 160.3 Nu 229.3
 10. The lens of claim 8 having values substantially as listed below: R1.217fR2.439fR3.213fR4.148ft1.051ft2.028fS1.0004fS2.093f nD11.620nD21.673 Nu 160.3 Nu 232.2
 11. The lens of claim 8 having values substantially as listed below: R1.208fR2.416fR3.203fR4.143ft10.45ft2.028fS1.0005fS2.093fnD11.620 nD21.720 Nu 160.3 Nu 229.3
 12. The lens of claim 8 having values substantially as listed below: R1.211fR2.424fR3.204fR4.143ft1.046ft20.29fS1.0005fS20.92fnD11.620 nD21.720 Nu 160.3 Nu 229.3
 13. The lens of claim 8 having values substantially as listed below: R1.211fR2.424fR3.203fR4.143ft1.045ft2.029fS1.0005fS2.093fnD11.620 nD21.720 Nu 160.3 Nu 229.3
 14. The lens of claim 8 having values substantially as listed below: R1.211fR2.424fR3.204fR4.143ft1.046ft2.029fS1.0005fS2.093fnD11.620 nD21.720 Nu 160.3 Nu 229.3
 15. A symmetrical lens having four singlet meniscus elements symmetrical about and concave Toward a central stop, the first and second elements having radii, proceeding toward the center, R1, R2, R3 and R4, and thicknesses, proceeding toward said center, t1 and t2, said lenses being spaced apart by a space S1 and said second lens being spaced from said center by a space S2, said radii, thicknesses, and spaces being expressed as a fraction of the focal length f falling within the ranges listed below and said elements being of glass having characteristic refractive indices nD1 and nD2 and Abbe numbers Nu 1 and Nu 2 falling within the ranges listed in the table below: .028f < or = R1 < or = .217f.416f < or = R2 < or = .439f.203f < or = R3 < or = .213f.143f < or = R4 < or = .148f0.45f < or = t1 < or = .051f0.28f < or = t2 < or = .030f.0004f < or = S1 < or = .0005f.092f < or = S2 < or = .095f1.620 Congruent nD11.673 < or = nD2 < or = 1.72060.3 Congruent Nu 1 29.3 < or = Nu 2 < or = 32.2
 16. A retroreflective lens for use at or near unit magnification having first and second singlet meniscus elements and a plano mirror, said elements being concave toward said mirror and having radii, proceeding toward said mirror, R1, R2, R3, and R4, and thicknesses, proceeding toward said mirror, t1 and t2, said first element being separated from said second element by a space S1, and said second element being separated from said mirror by a space S2, said radii, thicknesses and spaces being expressed as a fraction of the focal length f, falling within the ranges listed below, and said elements being of glass having characteristic refractive indices, nD1 and nD2, and Abbe numbers Nu 1 and Nu 2, falling within the ranges listed in the table below. .208f < or = R1 < or = .217f.416f < or = R2 < or = .439f.203f < or = R3 < or = .213f.143f < or = R4 < or = .148f.045f < or = t1 < or = .051f.028f < or = t2 < or = .030f.0004f < or = S1 < or = .0005f.092f < or = S2 < or = .095f1.620 Congruent nD11.673 < or = nD2 < or = 1.72060.3 Congruent Nu 1 29.3 < or = Nu 2 < or = 32.2 